The first trimester is when your baby’s major organs, facial features, and nervous system begin forming, which makes it the most sensitive window for outside interference. What you eat, drink, apply to your skin, and expose your body to all matter more during these first 12 weeks than at almost any other point in pregnancy. Here’s what to avoid and why.
Alcohol Has No Safe Threshold
There is no known safe amount of alcohol at any point in pregnancy, and the first trimester carries specific risks. Alcohol use in the first three months can cause abnormal facial features in the baby, a hallmark of fetal alcohol spectrum disorders. Because many people don’t realize they’re pregnant right away, early exposure is common, but once you know, stopping immediately is what matters. The CDC is clear on this: there is no safe amount, and there is no safe time.
Caffeine: Stay Under 200 mg a Day
You don’t have to give up coffee entirely. The American College of Obstetricians and Gynecologists considers moderate caffeine intake, defined as less than 200 mg per day, unlikely to be a major contributing factor in miscarriage or preterm birth. That’s roughly one 12-ounce cup of brewed coffee. Keep in mind that caffeine also shows up in tea, chocolate, soft drinks, and energy drinks, so you may need to add things up throughout the day.
Certain Fish and Raw Seafood
Fish is actually recommended during pregnancy for its omega-3 content, but seven types carry mercury levels high enough to warrant complete avoidance: king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish, and bigeye tuna. Mercury can damage a developing nervous system even in small amounts.
The FDA recommends eating 8 to 12 ounces per week of lower-mercury seafood (like salmon, shrimp, tilapia, or pollock), with a single serving during pregnancy being about 4 ounces, roughly the size of your palm. Raw or undercooked fish, including sushi made with raw seafood, also carries bacterial and parasitic risks that are harder for your immune system to handle right now.
Soft Cheeses and Deli Meats
Listeria is a bacterium that most healthy adults barely notice, but during pregnancy it can cause miscarriage, stillbirth, premature delivery, or serious health problems for the newborn. You might only feel mild, flu-like symptoms or nothing at all, while the infection quietly reaches the baby through the placenta.
The highest-risk foods include soft cheeses made from unpasteurized milk, such as queso fresco, queso blanco, and traditional brie or camembert. Notably, some queso fresco-style cheeses carry risk even when made from pasteurized milk due to the way they’re processed. Deli meats and hot dogs should be heated until steaming before you eat them, since refrigeration alone doesn’t kill listeria.
Over-the-Counter Painkillers (Especially Ibuprofen)
Reaching for ibuprofen or other anti-inflammatory painkillers is second nature for most people, but these medications have been linked to an increased chance of miscarriage, particularly when taken around the time of conception or over a prolonged period. The relationship is difficult to pin down precisely because miscarriage has many possible causes, but the association is consistent enough that most providers advise against it. Acetaminophen (Tylenol) is generally considered the safer option for pain relief during pregnancy, though you should still use the lowest effective dose.
Skincare Ingredients to Swap Out
Retinoids are the big one. Prescription tretinoin (often used for acne) should not be used during pregnancy. The same goes for hydroquinone, a common skin-bleaching ingredient that absorbs through the skin in significant amounts. Minoxidil, used for hair regrowth, also falls into the “avoid” category. Cosmetic Botox, while not linked to confirmed harm, isn’t medically necessary and isn’t recommended during pregnancy.
If your skincare routine includes any prescription-strength acne or anti-aging products, check the active ingredients before continuing. Many people switch to gentler routines built around vitamin C serums, hyaluronic acid, and mineral sunscreen for the duration of pregnancy.
Hot Tubs, Saunas, and Hot Yoga
Raising your core body temperature above about 38.9°C (102°F) during the first trimester increases the risk of neural tube defects, which affect the brain and spinal cord. Animal studies consistently show that a core temperature elevation of just 2°C above baseline, regardless of the heat source, is the critical threshold for risk. Hot tubs, saunas, hot yoga, and hot Pilates can all push you past that point. A warm bath is fine as long as you’re not submerging yourself in very hot water for extended periods. If your skin turns red and you start to feel uncomfortably warm, you’ve gone too far.
High-Risk Exercise and Activities
Exercise during pregnancy is encouraged, but the first trimester is a good time to drop anything with a meaningful fall or collision risk. ACOG specifically names contact sports like ice hockey, boxing, soccer, and basketball, along with activities where falls are likely: downhill skiing, water skiing, surfing, off-road cycling, gymnastics, horseback riding, and skydiving. Scuba diving is off the table for the entire pregnancy because of pressure changes that can affect the baby’s circulation.
If you exercise at altitude, stay below 6,000 feet unless you already live at that elevation. In general, avoid jerky, bouncy, or high-impact movements, and skip any position that has you lying flat on your back for long stretches. Walking, swimming, stationary cycling, and prenatal yoga (not the heated kind) are all solid options that carry very little risk.
Cat Litter and Garden Soil
Toxoplasmosis is a parasitic infection that passes through cat feces and contaminated soil. If the parasite enters your bloodstream during pregnancy, it can cross the placenta and cause hearing loss, intellectual disability, blindness, or brain and eye problems that may not appear until years after birth. An estimated 300 to 4,000 fetuses in the U.S. are infected each year.
The practical advice is straightforward: have someone else handle the litter box if at all possible. If you must do it yourself, wear disposable gloves, wash your hands thoroughly afterward, and change the litter daily, since the parasite doesn’t become infectious until one to five days after being shed. Wear gloves while gardening or handling sandbox soil, keep indoor cats indoors, feed cats only commercial food (never raw meat), and don’t adopt a new cat while you’re pregnant.
Herbal Teas and Supplements
“Herbal” and “natural” don’t mean safe during pregnancy. Some herbs can stimulate uterine contractions or disrupt hormonal balance. Chamomile tea, for instance, is widely seen as harmless, but large quantities have been associated with higher rates of preterm labor and miscarriage and may affect fetal circulation. A single cup occasionally is likely fine, but daily heavy consumption is a different story.
Other herbs commonly flagged include licorice root, dong quai, blue and black cohosh, and pennyroyal. Because herbal supplements aren’t regulated the same way medications are, their potency can vary widely between brands. If an herbal product doesn’t have clear safety data during pregnancy, the safer path is to skip it until after delivery.
Smoking and Secondhand Smoke
Smoking during the first trimester restricts oxygen and nutrient flow to the developing embryo and is linked to higher rates of miscarriage, ectopic pregnancy, and placental problems. Secondhand smoke carries many of the same risks. If you smoke, the first trimester is the most impactful time to stop, and if people around you smoke, ask them to do it outside and away from shared spaces.